<?php
echo sqrt(9),"\n";  //开平方
echo cos(60*pi()/180),"\n";  //余弦，参数的单位是弧度
echo cos(deg2rad(60)),"\n";//度数转弧度
echo pow(3,2),"\n";//3的平方
echo round(3.1415926,1),"\n";  //保留一位小数
echo round(3.1415926,3),"\n";  //保留三位小数